The field of the invention is mixers. In many applications, it is necessary to mix two materials together. For example, in manufacturing urethane or epoxy products, a hardener must be mixed with a base material. Similarly, it is often necessary to mix e.g., paints and thinners or to mix other hardeners, solvents, emulsifiers, dyes, etc. with one or more other materials, in any range of proportions.
In the past, various dynamic mechanical mixers have used rotors spinning within a mixing chamber. In other applications, impingement mixers have been used to achieve mixing by spraying or injecting one stream of material into another stream of material in a turbulent flow. However, impingement mixers are limited to approximately a 1:1 ratio of materials, as well as to materials having relatively low viscosities. So called static mixers which achieve varying degrees of material mixing by flowing the materials over fixed blades, have also been used.
Generally, dynamic mechanical mixers using a spinning mechanical rotor are advantageous due to their high mixing efficiency, wide range of mixing ratios and materials that they can handle, as well as their relatively compact and simple designs and high output rates.
On the other hand, dynamic mechanical mixers typically must be flushed and cleaned with toxic solvents such as methylene chloride, trichloroethylene and others, to clean the mixing chamber and mechanical parts in between mixing batches of urethane, epoxy, etc. Unfortunately, while the materials being mixed, for example, urethane, are relatively non-toxic and non-polluting, the cleaning solvents are highly volatile, toxic and contribute significantly to air pollution. These solvents are also very costly to purchase, handle, and dispose of. In addition, relatively large volumes of solvents are required for mixer cleaning. The used solvents are potentially very damaging to the air and ground environment.
A wide range of products such as computer cases, spas, wheels, bowling balls, gaskets, interior automobile parts, etc. are made from urethanes, isocyanates and other materials which require multiple part mixing. Consequently, the mass production manufacturing operations for these products presently use relatively large volumes of solvents to flush and clean mixing equipment. Since cleaning solvents contribute to air pollution, and because restrictions on their use is currently under consideration by government agencies such as the Southern California Air Quality Management District, there is a great need for alternative mixers or cleaning methods in many manufacturing industries.